Why do the last Cheerios in the bowl cuddle up?
The “Cheerios effect”
Why the last few Cheerios in your bowl clump together and cling to the edge.
Floating cereal bends the surface of the milk slightly. Two Cheerios next to each other each sit in a dip, and both slide towards the lower point between them.
The same physics explains how some insects and tiny objects float and gather on water. Your breakfast is a surface-tension demo.
Cereal is social. It just wants to be together.